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[O] Pure Biology Smart Guides

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  1. I. PRINCIPLES OF BIOLOGY

    2. Cells
    2 Topics
  2. 3. Movement of Substances
    1 Topic
  3. 4. Nutrients
    4 Topics
  4. 5. Enzymes
    2 Topics
  5. II. MAINTENANCE AND REGULATION OF LIFE PROCESSES
    6. Nutrition in Humans
    4 Topics
  6. 7. Nutrition in Plants
    2 Topics
  7. 8. Transport in Humans
    5 Topics
  8. 9. Transport in Plants
    4 Topics
  9. 10. Respiration in Humans
    5 Topics
  10. 11. Excretion in Humans
    4 Topics
  11. 12. Homeostasis
    3 Topics
  12. 13. Nervous System
    2 Topics
  13. 14. Human Eye
    2 Topics
  14. 15. Hormones
    2 Topics
  15. III. CONTINUITY OF LIFE
    16. Cell Division
    3 Topics
  16. 17. Reproduction in Plants
    3 Topics
  17. 18. Reproduction in Humans
    5 Topics
  18. 19. Heredity
    6 Topics
  19. 20. Molecular Genetics
    2 Topics
  20. IV. MAN AND HIS ENVIRONMENT
    21. Ecology
    5 Topics
  21. 22. Our Impact on the Ecosystem
    2 Topics
Chapter 3, Topic 3
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Carbohydrates

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Carbohydrates [CnH2mOm]

Monosaccharides(reducing sugars)Disaccharides(reducing sugars)Polysaccharides
GlucoseMaltoseStarch
FructoseSucrose?Glycogen
galactoseLactoseCellulose

Condensation reaction: It is a chemical reaction in which two simple molecules are joined together to forma larger molecule with the removal of one molecule ofwater.

Hydrolysis: It is a reaction in which a water molecule is needed to break up a complex molecule into simple molecules.

Benedict’s test (reducing sugars)

  1. Add 2 cm3 of Benedict’s solution to 2 cm3 of foodsample in a test tube.
  2. Shake the mixture.
  3. Heat the contents in a boiling water bath for 5minutes

Iodine test (starch)

  1. Add 2 cm3 of food sample to a clean test tube.
  2. Add a few drops of iodine solution to the test tube.
Glycogen and starch are suitable as storage materials in cells because: They are insoluble in water, so they do not change the water potential in the cells.They are large molecules which cannot diffuse through cell membranes, so they will not be lost from the cell.They can be easily hydrolysed to glucose when needed, for example, in tissue respiration.Their molecules have compact shapes so they occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule  
Carbohydrates are needed: to provide energy for cell activitiesto form supporting structures (e.g. cell wall)for conversion into other organic compounds (e.g. amino acids and fats)to form nucleic acids (e.g. DNA)to synthesise lubricantsto synthesise nectar in flowers